Propellant composition with a hydroxy-terminated copolymer-binder-catalyst of butadiene and acrylate

ABSTRACT

The copolymers of carboranyl methyl acrylate and butadiene and pertinent solid propellant formulations are disclosed. The copolymers serve as a binder for solid propellant compositions and also serve to increase the burning rate of solid propellants wherein used. The copolymers are produced in an organic solvent when polymerization is initiated by an azo type initiator selected from the initiators consisting of azo-bis-(2-methyl-5-hydroxyvaleronitrile), azo-bis-(hydroxyethyl-2-methyl propionate), and azo-bis-(2-methyl-3-hydroxypropionitrile).

Unite States Patent 1191 Baldwin et al.

[ Dec. 25, 1973 1 PROPELLANT COMPOSITION WITH A HYDROXY-TERMINATEDC()POLYMElR-BINDER-CATALYST 0F BUTADIENE AND ACRYLATE [75] Inventors:Mart G. Baldwin, Newtown, Pa.;

Samuel F. Reed, Jr., Huntsville, Ala.

[73] Assignee: Rohm and Haas Company [22] Filed: May 13, 1971 21 Appl.No.: 143,274

Related US. Application Data [60 bivigid'fitfsir. No. 849,255,.ITI1 31,1969.

UNITED STATES PATENTS 3,183,216 5/1965 Cohen et al 149/19 UX Sayles149/42 X Lampert 149/42 X Primary Examiner-Stephen J. Lechert, Jr.Attorney-Harry M. Saragovitz et a1.

[57] ABSTRACT The copolymers of carboranyl methyl acrylate and butadieneand pertinent solid propellant formulations are disclosed. Thecopolymers serve as a binder for solid propellant compositions and alsoserve to increase the burning rate of solid propellants wherein used.

The copolymers are produced in an organic solvent when polymerization isinitiated by an azo type initiator selected from the initiatorsconsisting of azo-bis-(Z-methyl-S-hydroxy-valeronitrile),aZo-bis-(hydroxyethyl-Z-methyl propionate), andazo-bis-(2-methyl-3-hydroxypropionitrile).

2 Claims, No Drawings PROPELLANT COMPOSITION WITH A HYDROXY-TERMINATEDCOPOLYMER-BINDER-CATALYST OF BUTADIENE AND ACRYLATE CROSS REFERENCE TORELATED APPLICATION This is a division of application Ser. No. 849,255,filed July 31, 1969.

BACKGROUND OF THE INVENTION:

The burning rates of solid propellants can be increased by introductionof certain additives. Many carborane derivatives have been utilized asadditives for this purpose, usually in the form of liquids in whichstate they also serve as plasticizing agents. In the liquid state thecarboranes exhibit the inherent disadvantages characteristic of liquidadditives such as loss by evaporation, migration, etc.; andconsequently, the propellant systems suffer, particularly on long termstorage.

Thus, a need exists for a modified form of carborane which form is notsubject to being lost by evaporation or migration from a storedpropellant composition.

An object of this invention is to provide a liquid copolymer of acarborane additive and a binder material which is not lost byevaporation or migration from a propellant composition whereincontained.

Another object is to provide a copolymer which is ca pable of beingcured to a rubber-like state.

A further object is to provide a propellant formulation having a bindercombined with a carborane additive which is effective in increasing theburning rate of a solid propellant composition wherein used.

SUMMARY OF THE INVENTION Carboranyl methyl acrylate (CMA) iscopolymerized with butadiene in an inert organic solvent after thepolymerization reaction is initiated by a suitable initiator such as oneselected from the initiators consisting ofazo-bis-(2-methyl-5-hydroxy-valerqnitrile), azo-bis-(Z-methyl-3-hydroxy-propionitrile), and aZobis-(hydroxyethyl-Z-inethylpropionate). The liquid copolymer is characterized by its molecularweight which is preferably in the range of about 3,500, its hydroxy-endgroup content of about 0.60 percent and' its boron content of about 13.5percent. The liquid copolymer functions to increase the burning rate ofsolid propellant compositions as well as functions as a binder for thecomposition wherein used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The copolymer formed byreaction of butadiene with carboranyl methyl acrylate is useful as abinder and also as a burning rate catalyst for solid propellantcompositions.

The liquid copolymer is characterized by its preferred molecular weightofabout 3,500, its hydroxyend group content of about 0.60 percent andits boron content of about l3 .5 weight percent. Theliquidpolymer ofbutadiene and carboranyl methyl acrylate (CMA) is produced by aprocedure as described by the descriptive technique set forth below asExample 1. Example II sets forth a test propellant composition utilizingthe liquid copolymer.

The Butadiene-CMA weight ratio may be varied from approxiamtely 1:5 to19:1 in preparative procedures.

The copolymers of this invention are tested ina propellant formulationand compared with a formulation utilizing only butadiene. The copolymerincludes those containing 5, 10, 15, 20, and about 50 weight percentCMA.

EXAMPLE I PROCEDURE FOR POLYMERIZATION OF BU- TADIENE AND CARBORANYLMETHYL ACRY- LATE (CMA): To a glass high-pressure reactor (Aerosol tube)is introduced 30 ml of dioxane, 4.88 g. (0.02 moles) carboranyl methylacrylate (CMA) and 1.65 g. (0.0066 moles)azo-bis-(2-methyl-5-hydroxyvaleronitrile) (AMHV). The reactor isattached to a vacuum line and deaerated by three alternate freezethawcycles. At this point 10.8 g. (0.2 moles) of butadiene is condensed intothe reactor, and the reaction is removed from the vacuum line and placedin an oil bath at 6667C. Heating is continued for a period of 72 hours.On cooling, the reactor is vented, the solvent removed by evaporation,and the copolymer reprecipitated by dissolving in ether followed by theaddition of methanol. After decanting the solvents, the copolymer isstripped of excess solvents on a rotary evaporator and finally dried at7075C. under reduced pressure (1 mm) for a period of 24 hours. Theliquid copolymer is then characterized by its molecular weight,hydroxy-end group content and elemental analysis. These values are:molecular weight 3500, hydroxy end group content 0.60, boron 13.5percent (calculated 14.05%).

EXAMPLE II The propellant test composition set forth below illustratesthe use of the copolymer of this invention. The burning rates for thetest composition are set forth in Table III wherein the rates arecompared with a propellant wherein butadiene in like amount percent byweight is the standard.

Butadiene/CMA copolymer binder 10.0 wt.

Isodecyl Pelargonate plasticizer 10.0

Aluminum Powder 10.0

Ammonium Perchlorate (56a) 70.0

Table I provides data for preparation of butadiene- CMA Copolymers.Polymerization temperatures may conveniently be maintained in the rangeof 6080C. Reaction times may vary between 24-120 hours. The preferredrange for reaction is about 72 hours.

Physical property data on the copolymers is given in Table II.

Burning rate data for the propellant test compositions of EXAMPLE II isset forth under Table III. The data indicates that carborane included aspart of the propellant binder is effective in increasing the burningrate.

TABLE I Experimental Data for Preparation of Butadiene-CMA Copolymers:Temp., 66-67 0.; time, 72 hours Weight AMHV, Molar ratio Solvent,polymer, Percent Number Butadiene, grams CMA, grams moles of monomers 30ml. grams yield 1 10.8 (0.2 mole). 4.88 (0.02 mole). 0066 10/1 Dloxane.8. 0 51 10.8 2 mol 4.88 (0.02 mole) 0 0066 10/1 Toluene 7,0 50

10.8 (0.2 mole). 4.88 (0.02 mole). 0 0066 10/1 DMF. 6, 1 39 10.8 (0.2mole). 9.76 (0.04 mole). 0 0072 6/1 Dioxan 8. 8 43 10.8 (0.2 mole) 14 64(0.06 mole). 0 0078 3.3/1 -.d0 11. 3 44 19.0 (0.35 mole) 1 0 (0.0044 mol0 0107 87. 5/1 .do 11, 8 59 18.0 (0.33 mole) 2 0 (0.0088 mole). 0. 010337. 5/1 do 12, 1 60 17.0 (0.32 mole). 8.0 (0.0131 mole). 0.0098 24/1 o11, 9 59 15.0 (0.28 mole)" 5.0 (0.022 mole) 0.009 9, 7 g

TABLE 11 Physical Property Date on Butadiene-CMA Copolymers MolecularWeight '/r OH "H3 in Polymer No. Weight Calcd*/Found Calc'd. "/Found 1.3500 0.97 0.60 14.05 13.5 2. 3200 1.06 0.95 14.05 8.4 3. 2900 1.17 1.0214.05 11.0 4. 3700 0.92 0.84 21.65 15.8 5. 3000 1.13 0.62 24.7 20.4 6.3200 1.06 1.36 2.32 2.00 7. 3300 1.03 1.31 4.69 4.20 8. 3600 0.94 1.04.02 7.8 9. 2600 1.31 1.04 10.07 8.1

* Calculated OH content is based on observed molecular weight, with theassumption that each molecule contains two hydroxyl groups. Based onmonomer charge.

TABLE 111 Burning Rate Data on Butadiene-CMA Copolymers in PropellantFormulations copolymer Boron Burning Rate (in/sec) No. Content (71' of800-824 1600-1615 propellant) psi psi Standard 0 0.501 0.797 6 0.200.529 0.816 7 0.42 0.542 0.858 8 0.78 0.558 0.910 9 0.81 0.660 1.033

The copolymers of this invention include those c0- polymers containingfrom about 5 to about 50 weight percent carboranyl methyl acrylate withthe remaining weight percent of copolymer being reacted butadiene. Theamount of the copolymer when used in propellant formulations can varyfrom about 5 to about 30 weight about 10 weight percent binder doesprovide lower burning rate control as desired. However, the use of ahigher weight percent binder having a higher carboranyl methyl acrylatecontent is preferred if a high burning rate propellant is desired.

We claim:

1. A propellant composition comprising isodecyl pclargonate plasticizer;aluminum powder; ammonium percent. The burning rates of the propellantincrease perchlorate; and the hydroxyl terminated-copolymers ofbutadiene and carboranyl methyl acrylate prepared by the method whichcomprises reacting together carboranyl methyl acrylate; polymerizationinitiator selected from azo-bis-(2-methyl-5-hydroxyvaleronitrile),azo-bis-(Z-methyl-S-hydroxypropionitrile), andazo-bis-(hydroxyethyl-Z-methyl propionate) in an inert organic solvent,said solvent selected from dioxane, toluene, and dimethyl formamide; andbutadiene at a reaction temperature in the range of about 70C to about75C and for a reaction time period from about 24 hours to about 120hours to form said copolymers; effecting solvent removal from saidcopolymers; and drying said copolymers at reduced pressure in the rangeof about 1 millimeter, said butadiene to carborafiykm thyl acolate n lestsqmlafiqiahqyt iii to about 19:1 to yield hydroxy terminatedcopolymers characterized by a molecular weight range from about 2,600 toabout 3,700, a hydroxy-end group content in the range from about 0.60weight percent to about 1.36 weight percent, a boron content in therange of about 2 to about 20.4 weight percent, and said copolymerscontaining from about 5 to about weight percent carboranyl methylacrylate and said propellant composition containing up to about 30weight percent of said copolymers. v w w 2. The propellant compositionof claim 1 and wherein said composition is comprised of said copolymersin the amount of about 10.0 weight percent, iso- 50 decyl perlargonateplasticizer in the amount of about 10.0 weight percent, and ammoniumperchlorate in the amount of about 70.0 weight percent.

UNITED STATES PATENT OFFICE (IERTIFICATE 0F CORECTION December 25, 1973Patent No; 378ll78 Dated Inventor-(s) Mart G. Baldwin et a1.

- It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the cover sheet, in the heading, itemUB] Assignee:

"Rohm and Haas Company should read United States of America asrepresented by the Secretary of the Army Signed and sealed this lLrthday of May 19714..

i r At te st EDWARD M .FLET CHER J R I C MARSHALL DANN Attesting OfficerCommissioner of Patents FORM PO-wSQ 9-68) USCOMM-DC wan-pee i U.S.GOVERNMENT DRIN HNG O FIlClE I96! 0-JGI-3M.

NI ED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN patent 3,7 7 DatedDecember 25, 1973 Mart G. Baldwin et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the cover sheet, in the heading, item73j Assignee:

"Rohm and Haas Company" should read United States. of

America as represented by the Secretary-of the Signed and sealed thislhth day ofMay 197L (SEAL) I t Attest:

EDWARD I I.FIJ:ITCHER,JR. I C. MARSHALL DANN Attesting OfficerCommissioner of Patents uscoMM-Dc we're-P09 Y [1.5. GOVERNMENT {RIP IHNGQUICK I!" O-fliI-"l,

Form so-wso was)

2. The propellant composition of claim 1 and wherein said composition iscomprised of said copolymers in the amount of about 10.0 weight percent,isodecyl perlargonate plasticizer in the amount of about 10.0 weightpercent, and ammonium perchlorate in the amount of about 70.0 weightpercent.